Femtosecond laser microfabrication of subwavelength structures in photonics

Abstract

This paper describes experimental and numerical results of the plasma-assisted microfabrication of subwavelength structures by means of point-by point femtosecond laser inscription. It is shown that the spatio-temporal evolution of light and plasma patterns critically depend on input power. Subwavelength inscription corresponds to the supercritical propagation regimes when pulse power is several times self-focusing threshold. Experimental and numerical profiles show quantitative agreement.

Microstructured waveguides in z-cut LiNbO_3 by high-repetition rate direct femtosecond laser inscription

“…A more detailed description of the experimental setup used for inscription can be found in [14]. Note that the better the focusing of the fs beam onto the sample to be inscribed, the lower the pulse energy above which a continuum light is produced within the material for a given inscription depth [23,24]. In borosilicate (BK7) glass, using an in-house designed, long working distance, oil-immersed microscope objective with an effective NA of 1.2 [25], we measured this energy threshold to be approximately 12 nJ at an inscription depth of 0.5 mm, whereas in LiNbO 3 (and with the 1.25 NA of the commercial objective) the threshold was three times higher at an inscription depth of approximately 0.25 mm.…”

Waveguide fabrication in lithium-niobo-phosphate glasses by high repetition rate femtosecond laser: route to non-equilibrium material’s states

“…A range of photonic structures and devices has been demonstrated recently based on permanent modification of refractive index after fs inscription (see e.g. [2,3] and references therein). This enabling technology significantly expands the technological boundaries for direct fabrication of photonics structures in a wide variety of materials, as it allows modification of virtually any non-photosensitive transparent material, thus opening the door to numerous practical applications [2].…”

Multi-threaded parallel simulation of non-local non-linear problems in ultrashort laser pulse propagation in the presence of plasma

“…In this paper we consider a parallel numerical solution for a specific model which describes femtosecond laser pulse propagation in transparent media. In this model, GNLSE is coupled to the Drude model of plasma resulting from multi-photon and avalanche ionisation processes [1,2,3]. However our approach can be extended to similar models.…”

“…Coupling between the GNLSE and the Drude model of plasma results in impossible straightforward parallel implementation of such model due to non-locality. Hence, efficient use of GPU's parallel resources requires radical revision of the current pipelined method presented in [1,2].…”

“…We compare performance of the multithreaded parallel code implemented for Nvidia Graphics Processing Units (GPU) using CUDA programming interface [4] with a serial CPU version similar to that described in [1,2]. Coupling between the GNLSE and the Drude model of plasma results in impossible straightforward parallel implementation of such model due to non-locality.…”